U.S. patent application number 13/353883 was filed with the patent office on 2012-07-26 for substrate processing method and substrate processing apparatus.
Invention is credited to Naozumi FUJIWARA, Masahiko KATO, Katsuhiko MIYA.
Application Number | 20120186275 13/353883 |
Document ID | / |
Family ID | 46527783 |
Filed Date | 2012-07-26 |
United States Patent
Application |
20120186275 |
Kind Code |
A1 |
KATO; Masahiko ; et
al. |
July 26, 2012 |
SUBSTRATE PROCESSING METHOD AND SUBSTRATE PROCESSING APPARATUS
Abstract
A cooling gas discharge nozzle 7 is arranged above an initial
position P(Rin) distant from a rotation center P(0) of a substrate
W toward the outer edge of the substrate W and supplies a cooling
gas to the initial position P(0) of the rotating substrate W to
solidify DIW adhering to an initial region including the initial
position P(Rin) and the rotation center P(0). Following formation
of an initial solidified region FR0, a range to be solidified is
spread toward the outer edge of the substrate W and all the DIW
(liquid to be solidified) adhering to a substrate surface Wf is
solidified to entirely freeze a liquid film LF.
Inventors: |
KATO; Masahiko; (Kyoto,
JP) ; FUJIWARA; Naozumi; (Kyoto, JP) ; MIYA;
Katsuhiko; (Kyoto, JP) |
Family ID: |
46527783 |
Appl. No.: |
13/353883 |
Filed: |
January 19, 2012 |
Current U.S.
Class: |
62/64 ;
62/374 |
Current CPC
Class: |
H01L 21/67051 20130101;
H01L 21/02052 20130101 |
Class at
Publication: |
62/64 ;
62/374 |
International
Class: |
F25D 31/00 20060101
F25D031/00; F25D 17/04 20060101 F25D017/04; F25D 17/02 20060101
F25D017/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 20, 2011 |
JP |
2011-009906 |
Claims
1. A substrate processing method, comprising: a solidifying step of
solidifying a liquid to be solidified by supplying a cooling gas,
which has a temperature lower than a solidification point of the
liquid to be solidified, from a nozzle to a surface of a substrate
to which the liquid to be solidified is adhering while holding the
substrate substantially horizontally and rotating the substrate
about a vertical axis; and a melting step of melting and removing
the liquid solidified by the solidifying step, wherein the
solidifying step includes: an initial solidifying step of supplying
the cooling gas from the nozzle, which is arranged above an initial
position distant from the rotation center of the substrate toward
the outer edge of the substrate, to the initial position so as to
solidify the liquid to be solidified in an initial region extending
from the initial position to a rotation center of the substrate;
and a nozzle moving step of relatively moving the nozzle toward the
outer edge of the substrate while supplying the cooling gas from
the nozzle after the initial solidifying step.
2. The substrate processing method according to claim 1, wherein:
the initial position is closer to the rotation center of the
substrate than a middle position between the rotation center of the
substrate and the outer edge of the substrate.
3. The substrate processing method according to claim 1, wherein:
the cooling gas is supplied to the surface of the substrate from a
gas discharge port provided at a leading end part of the nozzle in
the solidifying step; and a distance from the rotation center of
the substrate to the initial position is equal to or larger than
half the diameter of the gas discharge port.
4. The substrate processing method according to claim 1, wherein: a
relative movement of the nozzle is started in the solidifying step
after the elapse of a first time since the supply of the cooling
gas to the initial position.
5. The substrate processing method according to claim 1, wherein:
the supply of the cooling gas is stopped in the solidifying step
after the elapse of a second time since a movement of the nozzle to
a position above the vicinity of the outer edge of the substrate
was completed.
6. A substrate processing apparatus, comprising: a substrate holder
that holds a substrate, which has a surface to which a liquid to be
solidified is adhering, substantially horizontally; a rotator that
rotates the substrate held by the substrate holder about a vertical
axis; a cooling gas supplier including a nozzle relatively movable
along the surface of the substrate above the surface of the
substrate held by the substrate holder and adapted to supply a
cooling gas having a temperature than a solidification point of the
liquid to be solidified from the nozzle to the surface of the
substrate; and a mover that relatively moves the nozzle along the
surface of the substrate; wherein: the mover relatively moves the
nozzle toward the outer edge of the substrate after arranging the
nozzle above an initial position distant from a rotation center of
the substrate toward the outer edge of the substrate; and the
cooling gas supplier solidifies the liquid to be solidified in an
initial region, which extends from the initial position to the
rotation center of the substrate, by supplying the cooling gas from
the nozzle arranged above the initial position before a relative
movement of the nozzle from a position above the initial position
toward the outer edge of the substrate is started, and solidifies
the liquid to be solidified outside the initial region by supplying
the cooling gas from the nozzle after the relative movement of the
nozzle toward the outer edge of the substrate is started.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The disclosure of Japanese Patent Application No. 2011-9906
filed on Jan. 20, 2011 including specification, drawings and claims
is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to a substrate processing method of
and a substrate processing apparatus for removing contaminants such
as particles adhering to surfaces of various substrates such as
semiconductor wafers, glass substrates for photomasks, glass
substrates for liquid crystal displays, glass substrates for plasma
displays, and substrates for optical discs.
[0004] 2. Description of the Related Art
[0005] Conventionally, a freeze cleaning technique has been known
as one process for removing contaminants such as particles adhering
to substrate surfaces. In this technique, after a liquid film
formed on a surface of a substrate is frozen, this frozen film is
melted and removed to remove particles and the like together with
the frozen film from the substrate surface. For example, in the
technique disclosed in JP-A-2008-071875, after a liquid film is
formed by supplying DIW (deionized water) as a cleaning liquid to a
substrate surface, a nozzle for discharging a cooling gas is
scanned from a central part to an outer peripheral part of the
substrate to freeze the liquid film, and the frozen film is melted
and removed by supplying the DIW again, whereby particles are
removed from the substrate surface.
SUMMARY OF THE INVENTION
[0006] As a result of various experiments, the inventors of this
application found out a certain correlation between the temperature
of a frozen film and a particle removal rate. The finding is that
the particle removal rate can be further improved not only by
merely freezing a liquid film, but also by further reducing the
temperature of the frozen film. Accordingly, it is advantageous in
improving the particle removal rate to reduce the temperature of
the frozen film and improvements of liquid film cooling conditions
such as a reduction in the temperature of a cooling gas are being
studied.
[0007] However, since the nozzle is scanned from the central part
to the outer peripheral part of the substrate as described above in
an apparatus disclosed in JP-A-2008-071875, a cooling gas supply
time per unit area is shorter near the outer edge than in the
central part of the substrate and the temperature of the frozen
film near the outer edge is not reduced as compared to the central
part of the substrate. Thus, the temperature of the frozen film
becomes nonuniform between the central part and the vicinity of the
outer edge of the substrate, with the result that there has been a
problem of impairing in-plane uniformity of the removal rate.
[0008] Accordingly, to solve such a problem, it is thought to
extend the cooling time near the outer edge, for example, by
suppressing a nozzle moving speed near the outer edge. However,
extended time makes a total time required for a freeze cleaning
process of the substrate longer, which leads to a reduction in
throughput.
[0009] This invention was developed in view of the above problem
and an object thereof is to provide a technique capable of removing
particles and the like with excellent in-plane uniformity without
leading to a reduction in throughput in a substrate processing
method and a substrate processing apparatus for removing
contaminants such as particles adhering to a substrate surface.
[0010] In an aspect of the invention, a substrate processing method
comprises: a solidifying step of solidifying a liquid to be
solidified by supplying a cooling gas, which has a temperature
lower than a solidification point of the liquid to be solidified,
from a nozzle to a surface of a substrate to which the liquid to be
solidified is adhering while holding the substrate substantially
horizontally and rotating the substrate about a vertical axis; and
a melting step of melting and removing the liquid solidified by the
solidifying step, wherein the solidifying step includes: an initial
solidifying step of supplying the cooling gas from the nozzle,
which is arranged above an initial position distant from the
rotation center of the substrate toward the outer edge of the
substrate, to the initial position so as to solidify the liquid to
be solidified in an initial region extending from the initial
position to a rotation center of the substrate; and a nozzle moving
step of relatively moving the nozzle toward the outer edge of the
substrate while supplying the cooling gas from the nozzle after the
initial solidifying step.
[0011] In another aspect of the invention, a substrate processing
apparatus comprises: a substrate holder that holds a substrate,
which has a surface to which a liquid to be solidified is adhering,
substantially horizontally; a rotator that rotates the substrate
held by the substrate holder about a vertical axis; a cooling gas
supplier including a nozzle relatively movable along the surface of
the substrate above the surface of the substrate held by the
substrate holder and adapted to supply a cooling gas having a
temperature than a solidification point of the liquid to be
solidified from the nozzle to the surface of the substrate; and a
mover that relatively moves the nozzle along the surface of the
substrate; wherein: the mover relatively moves the nozzle toward
the outer edge of the substrate after arranging the nozzle above an
initial position distant from a rotation center of the substrate
toward the outer edge of the substrate; and the cooling gas
supplier solidifies the liquid to be solidified in an initial
region, which extends from the initial position to the rotation
center of the substrate, by supplying the cooling gas from the
nozzle arranged above the initial position before a relative
movement of the nozzle from a position above the initial position
toward the outer edge of the substrate is started, and solidifies
the liquid to be solidified outside the initial region by supplying
the cooling gas from the nozzle after the relative movement of the
nozzle toward the outer edge of the substrate is started.
[0012] According to the invention, the nozzle is relatively moved
toward the outer edge of the substrate to solidify all the liquid
to be solidified adhering to the surface of the substrate after the
liquid to be solidified adhering to the initial region is
solidified by supplying the cooling gas to the initial position
from the nozzle arranged above the initial position distant from
the rotation center of the substrate toward the outer edge of the
substrate. Thus, the end-point temperature of the solidified liquid
can be made uniform and particles and the like can be removed with
excellent in-plane uniformity without leading to a reduction in
throughput.
[0013] The above and further objects and novel features of the
invention will more fully appear from the following detailed
description when the same is read in connection with the
accompanying drawing. It is to be expressly understood, however,
that the drawing is for purpose of illustration only and is not
intended as a definition of the limits of the invention.
BRIEF DESCRIPTIONS OF THE DRAWINGS
[0014] FIG. 1 is a graph showing a relationship between liquid film
temperature and particle removal efficiency in the freeze cleaning
technique;
[0015] FIG. 2 is a diagram showing one embodiment of a substrate
processing apparatus according to this invention;
[0016] FIG. 3 is a diagram showing supply modes of a nitrogen gas
and DIW in the substrate processing apparatus of FIG. 2;
[0017] FIG. 4 is a diagram showing movement modes of arms in the
substrate processing apparatus of FIG. 2;
[0018] FIGS. 5A to 5C, 6A and 6B are views diagrammatically showing
operations of the substrate processing apparatus of FIG. 2;
[0019] FIGS. 7A to 7C, 8A to 8C are views relationships between
initial positions and initial solidified regions;
[0020] FIGS. 9A to 9C are views showing relationships between the
initial positions and end-point temperatures; and
[0021] FIG. 10 is a graph showing a relationship between the
initial position and an in-plane uniformity of the particle removal
efficiency.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Relationship Between Liquid Film Temperature and Particle Removal
Efficiency
[0022] Although a liquid film is frozen in the conventional freeze
cleaning technique, much consideration has not been given to liquid
film temperature after freezing. However, according to an
experiment by the inventors of this application using a liquid film
by DIW (liquid to be solidified), it was elucidated that particle
removal efficiency was improved not only by merely freezing the
liquid film, but also as the end-point temperature of the liquid
film after freezing decreased as shown in FIG. 1. Note that the
temperature of the liquid film before freezing and the temperature
of a solidified body obtained by freezing the liquid film are
collectively referred to as the "temperature of the liquid film" in
this specification.
[0023] FIG. 1 is a graph showing a relationship between liquid film
temperature and particle removal efficiency in the so-called freeze
cleaning technique and specifically showing a result obtained by
the following experiment. In this experiment, bare (state where no
pattern is formed) Si wafers (wafer diameter: 300 millimeter) are
selected as a representative example of substrates. Further,
evaluation is made for a case where substrate surfaces are
contaminated by Si debris (particle diameter: 0.08 micrometer or
larger) as particles.
[0024] First, wafers are forcibly contaminated using a
single-substrate processing apparatus (Spin Processor SS-3000
produced by Dai Nippon Screen MFG Co., Ltd.). Specifically, a
dispersion liquid in which particles (Si debris) are dispersed is
supplied to the wafers from a nozzle arranged to face the wafers
while the wafers are rotated. Here, the amount of the dispersion
liquid, the number of rotations of the wafer and a processing time
are appropriately so adjusted that the number of particles adhering
to the wafer surface is about 10000. Thereafter, the number
(initial value) of the particles adhering to the wafer surface is
measured. Note that the number of the particles is measured for an
area of the wafer excluding a 3 mm-peripheral area from the outer
periphery (edge cut) using a wafer inspection equipment SP1
produced by KLA-Tencor.
[0025] Subsequently, the following cleaning process is performed on
each wafer. First, DIW temperature-regulated to 0.5 degrees Celsius
is discharged for 6 seconds to the wafer rotating at 150 rpm to
cool the wafer. Thereafter, the discharge of the DIW is stopped and
the number of rotations of the wafer is maintained for 2 seconds,
whereby redundant DIW is spun off to form a liquid film. After
formation of the liquid film, the number of rotations of the wafer
is reduced to 50 rpm and a nitrogen gas of -190 degrees Celsius is
discharged to the wafer surface at a flow rate of 90 [L/min] by a
scan nozzle while the number of rotations of the wafer is
maintained. The nozzle is scanned back and forth between the center
and the end of the wafer for 20 seconds. Black rectangles in FIG. 1
correspond to the numbers of scans, and the result up to five scans
is shown in FIG. 1 with the leftmost black rectangle representing
one scan, the second leftmost one representing two scans, and so
forth. By changing the number of scans in this way, a temperature
after freezing is changed.
[0026] After the above cooling is finished, the number of rotations
of the wafer is set to 2000 rpm and DIW temperature-regulated to 80
degrees Celsius is discharged at a flow rate of 4.0 [L/min] for 2
seconds. Thereafter, the number of rotations of the wafer is set to
500 rpm and normal-temperature DIW as a rinsing liquid is supplied
at a flow rate of 1.5 [L/min] for 30 seconds to rinse the wafer.
Thereafter, the wafer is spin-dried by being rotated at a high
speed.
[0027] The number of particles adhering to the wafer surface having
a series of cleaning processes performed thereon in this way is
measured. Then, a removal rate is calculated by comparing the
number of particles after freeze cleaning and the initial number of
particles measured earlier (before the freeze cleaning process).
The graph shown in FIG. 1 is obtained by plotting data obtained in
this way.
[0028] As is clear from FIG. 1, the particle removal efficiency is
improved not only by merely freezing the liquid film, but also as
the end-point temperature of the liquid film after freezing
decreases. That is, a cleaning effect can be improved by, after the
DIW liquid film on the substrate is frozen by the cooling gas,
further cooling the frozen liquid film (solidified body) to reduce
the final end-point temperature. Further, to ensure in-plane
uniformity of the particle removal efficiency, it is important to
make the end-point temperature of the liquid film after freezing
substantially equal between the central part and the vicinity of
the outer edge of the wafer.
[0029] Here, the entire liquid film can be cooled to have a uniform
end-point temperature by repeating the back-and-forth scan movement
between the center and the end of the wafer as in the above
experiment. However, since repetition of the scan movement leads to
a reduction in throughput, the liquid film needs to be normally
frozen by one scan movement as disclosed, for example, in
JP-A-2008-071875. That is, it is required to form a solidified body
with a uniform end-point temperature for a short period of time by
one scan movement. Accordingly, in the following embodiment, after
a nozzle is first arranged at a position shifted toward the outer
edge of a wafer from a position above a rotation center of the
wafer and a liquid to be solidified in a given area is solidified,
the nozzle is relatively moved toward the outer edge, whereby a
solidification range spreads outward from the center of the wafer
to achieve the above object. Hereinafter, the embodiment will be
described in detail with reference to the drawings.
Embodiment
[0030] FIG. 2 is a diagram showing one embodiment of a substrate
processing apparatus according to this invention. FIG. 3 is a
diagram showing supply modes of a nitrogen gas and DIW in the
substrate processing apparatus of FIG. 2. FIG. 4 is a diagram
showing movement modes of arms in the substrate processing
apparatus of FIG. 2. This apparatus is a single-substrate
processing apparatus capable of performing a substrate cleaning
process to remove contaminants such as particles adhering to a
surface Wf of a substrate W such as a semiconductor wafer. More
specifically, the substrate processing apparatus performs a freeze
cleaning process for, after forming a liquid film on a substrate
surface Wf formed with a fine pattern and forming a solidified film
(solidified body) by freezing the liquid film, melting and removing
the solidified film to remove the particles and the like from the
substrate surface Wf together with the solidified film. The freeze
cleaning technique is not described in detail in this specification
since it is disclosed in many known literatures including
JP-A-2008-071875 described above.
[0031] This substrate processing apparatus includes a processing
chamber 1, and a spin chuck 2 for rotating the substrate W held in
a substantially horizontal posture with the surface Wf thereof
faced upward in this processing chamber 1. As shown in FIG. 3, a
disk-shaped spin base 23 is fixed to the upper end of a center
shaft 21 of this spin chuck 2 by a fastening part such as a screw.
This center shaft 21 is coupled to a rotary shaft of a chuck
rotating mechanism 22 including a motor. When the chuck rotating
mechanism 22 is driven in response to an operation command from a
control unit 4 for controlling the entire apparatus, the spin base
23 fixed to the center shaft 21 rotates about a central axis of
rotation AO.
[0032] A plurality of chuck pins 24 for gripping a peripheral edge
part of the substrate W stand near a peripheral edge part of the
spin base 23. Three or more chuck pins 24 may be provided to
reliably hold the circular substrate W. The chuck pins 24 may be
arranged at equal angular intervals along the peripheral edge part
of the spin base 23. Each of the chuck pins 24 includes a substrate
supporting part for supporting the peripheral edge part of the
substrate W from below and a substrate holding part for holding the
substrate by pressing the outer peripheral end surface of the
substrate W supported on the substrate supporting part. Each chuck
pin 24 can be switched between a pressing state where the substrate
holding part presses the outer peripheral end surface of the
substrate W and a releasing state where the substrate holding part
is separated from the outer peripheral end surface of the substrate
W.
[0033] The respective chuck pins 24 are set in the releasing state
when the substrate W is transferred to the spin base 23 while being
set in the pressing state when a cleaning process is performed on
the substrate W. When being set in the pressing state, the
respective chuck pins 24 grip the peripheral edge part of the
substrate W and the substrate W is held in the substantially
horizontal posture while being spaced apart from the spin base 23
by a predetermined distance. In this way, the substrate W is held
with its front surface (pattern-formed surface) Wf directed toward
above and its back surface Wb toward below.
[0034] A blocking member 9 is arranged above the spin chuck 2
constructed as described above. This blocking member 9 is in the
form of a circular plate having an opening in a central part.
Further, the lower surface of the blocking member 9 is a
surface-facing surface facing the surface Wf of the substrate W
substantially in parallel and is sized to have a diameter equal to
or larger than that of the substrate W. This blocking member 9 is
substantially horizontally attached to the lower end of a
supporting shaft 91. This supporting shaft 91 is held rotatably
about a vertical axis passing through the center of the substrate W
by an arm 92 extending in a horizontal direction. Further, a
blocking member elevating/rotating mechanism 93 is connected to the
arm 92.
[0035] The blocking member elevating/rotating mechanism 93 rotates
the supporting shaft 91 about the vertical axis passing through the
center of the substrate W in response to an operation command from
the control unit 4. The control unit 4 controls the movement of the
blocking member elevating/rotating mechanism 93 and rotates the
blocking member 9 in the same rotational direction and
substantially at the same rotational speed as the substrate W
according to the rotation of the substrate W held by the spin chuck
2. Further, the blocking member elevating/rotating mechanism 93
moves the blocking member 9 toward and conversely away from the
spin base 23 in response to an operation command from the control
unit 4. Specifically, the control unit 4 controls the movement of
the blocking member elevating/rotating mechanism 93 to lift the
blocking member 9 to a separated position (position shown in FIG.
2) above the spin chuck 2 when the substrate W is loaded into and
unloaded from the substrate processing apparatus and, on the other
hand, lower the blocking member 9 to a facing position set very
close to the surface Wf of the substrate W held by the spin chuck 2
when a specified process is performed on the substrate W.
[0036] As shown in FIG. 3, the supporting shaft 91 of the blocking
member 9 is hollow and a gas supply pipe 95 which is open in the
lower surface (substrate-facing surface) of the blocking member 9
is inserted into the supporting shaft 91. This gas supply pipe 95
is connected to a dry gas supply unit 61. This dry gas supply unit
61 is for supplying a nitrogen gas supplied from a nitrogen gas
supply source (not shown) to the substrate W and includes a mass
flow controller (MFC) 611 and an on-off valve 612. This mass flow
controller 611 can regulate the flow rate of the nitrogen gas with
high accuracy in response to a flow rate command from the control
unit 4. Further, the on-off valve 612 opens and closes in response
to opening and closing commands from the control unit 4 to
switchingly supply and stop the supply of the nitrogen gas having
the flow rate regulated by the mass flow controller 611. Thus, by
the control unit 4 controlling the dry gas supply unit 61, the
nitrogen gas having the flow rate regulated is supplied as a dry
gas for drying the substrate W from the gas supply pipe 95 toward a
space formed between the blocking member 9 and the surface Wf of
the substrate W at a proper timing. Note that although the nitrogen
gas is supplied as the dry gas from the dry gas supply unit 61 in
this embodiment, air or another inert gas may be supplied.
[0037] A liquid supply pipe 96 is inserted through the interior of
the gas supply pipe 95. A lower end part of this liquid supply pipe
96 is open in the lower surface of the blocking member 9, and a
liquid discharge nozzle 97 is provided at the leading end of the
liquid supply pipe 96. On the other hand, an upper end part of the
liquid supply pipe 96 is connected to a DIW supply unit 62. This
DIW supply unit 62 is for supplying normal-temperature DIW supplied
from a DIW supply source (not shown) as a rinsing liquid and
supplying high-temperature DIW heated to about 80 degrees Celsius
to the substrate W for a melting and removing process, and is
constructed as follows. Here, two pipe lines are provided for the
DIW supply source. A flow regulating valve 621 and an on-off valve
622 are inserted in the pipe line for a rinsing process which is
one of these pipe lines. The flow regulating valve 621 can regulate
the flow rate of the normal-temperature DIW with high accuracy in
response to a flow rate command form the control unit 4. Further,
the on-off valve 622 opens and closes in response to an opening and
closing command from the control unit 4 to switchingly supply and
stop the supply of the normal-temperature DIW having the flow rate
regulated by the flow regulating valve 621.
[0038] A flow regulating valve 623, a heater 624 and an on-off
valve 625 are inserted in another pipe line for the melting and
removing process. This flow regulating valve 623 regulates the flow
rate of the normal-temperature DIW with high accuracy in response
to a flow rate command from the control unit 4 and feeds the
regulated normal-temperature DIW to the heater 624. The heater 624
heats the fed normal-temperature DIW to about 80 degrees Celsius
and the heated DIW (hereinafter, referred to as "high-temperature
DIW") is fed out via the on-off valve 625. Note that the on-off
valve 625 switchingly supplies and stops the supply of the
high-temperature DIW by being opened and closed in response to
opening and closing commands from the control unit 4. In this way,
the normal-temperature DIW and the high-temperature DIW fed out
from the DIW supply unit 62 are discharged from the liquid
discharge nozzle 97 toward the surface Wf of the substrate W at
proper timings.
[0039] The center shaft 21 of the spin chuck 2 has a cylindrical
hollow and a cylindrical liquid supply pipe 25 for supplying the
rinsing liquid to the back surface Wb of the substrate W is
inserted through the interior of the center shaft 21. The liquid
supply pipe 25 extends up to a position proximate to the back
surface Wb that is the back surface Wb of the substrate W held by
the spin chuck 2, and a liquid discharge nozzle 27 for discharging
the rinsing liquid toward a central part of the back surface of the
substrate W is provided at the leading end of the liquid supply
pipe 25. The liquid supply pipe 25 is connected to the DIW supply
unit 62 described above and supplies the DIW as the rinsing liquid
toward the back surface Wb of the substrate W.
[0040] A clearance between the inner wall surface of the center
shaft 21 and the outer wall surface of the liquid supply pipe 25
serves as a gas supply path 29 having a ring-shaped cross section.
This gas supply path 29 is connected to the dry gas supply unit 61
and the nitrogen gas is supplied from the dry gas supply unit 61 to
a space formed between the spin base 23 and the back surface Wb of
the substrate W via the gas supply path 29.
[0041] As shown in FIG. 2, in this embodiment, a splash guard 51 is
so provided around the spin chuck 2 movably upward and downward
relative to the rotary shaft of the spin chuck 2 as to surround
around the substrate W held in the horizontal posture by the spin
chuck 2. This splash guard 51 is shaped to be rotationally
symmetrical with respect to the rotary shaft. By moving the splash
guide 51 upward and downward in a stepwise manner by driving a
guard elevating mechanism 52, the DIW for forming the liquid film,
the rinsing liquid, and other processing liquids supplied to the
substrate W for other purposes that fly apart from the rotating
substrate W can be sorted out and discharged to unillustrated
discharged liquid processing units from the interior of the
processing chamber 1.
[0042] A plurality of exhaust ports 11 are provided at a bottom
surface part of this processing chamber 1, and the internal space
of the processing chamber 1 is connected to an exhaust unit 63 via
these exhaust ports 11. This exhaust unit 63 includes an exhaust
damper and an exhaust pump and the amount of exhaust by the exhaust
unit 63 can be regulated by controlling a degree of opening of the
exhaust damper. The control unit 4 gives a command concerning the
amount of opening of the exhaust damper to the exhaust unit 63 to
regulate the amount of exhaust from the processing chamber 1 and
control temperature and humidity in the internal space.
[0043] In this substrate processing apparatus, a cooling gas
discharge nozzle 7 is so provided as to be able to discharge a
cooling gas for freezing the liquid film toward the surface Wf of
the substrate W held by the spin chuck 2. That is, the cooling gas
discharge nozzle 7 is connected to a cooling gas supply unit 64
constructed as follows. As shown in FIG. 3, the cooling gas supply
unit 64 includes a heat exchanger 641. A container 642 of the heat
exchanger 641 is in the form of a tank which stores liquid nitrogen
inside and is made of a material which can withstand liquid
nitrogen temperature, e.g. glass, quartz or HDPE (High Density
Polyethylene). Note that a double structure covering the container
642 by a heat insulating container may be adopted. In this case,
the outer container is preferably made of a material having high
heat insulation, e.g. foamable resin or PVC (Polyvinyl Chloride) to
suppress heat transfer between atmosphere outside the processing
chamber and the container 642.
[0044] The container 642 includes a liquid nitrogen feed port 643
through which the liquid nitrogen is introduced. This liquid
nitrogen feed port 643 is connected to a liquid nitrogen supply
source (not shown) via an on-off valve 644 and the liquid nitrogen
fed out from the liquid nitrogen supply source is introduced into
the container 642 when the on-off valve 644 is opened in response
to an opening command from the control unit 4. Further, a liquid
level sensor (not shown) is provided in the container 642, a
detection result by this liquid level sensor is input to the
control unit 4 and the opening and closing of the on-off valve 644
are controlled by a feedback control by the control unit 4 so that
the liquid level of the liquid nitrogen in the container 642 can be
controlled with high accuracy. Note that, in this embodiment, the
feedback control is so executed that the liquid level of the liquid
nitrogen becomes constant, whereby the temperature of the cooling
gas is stabilized.
[0045] A coil-shaped heat exchanger pipe 645 made of metal such as
stainless steel or copper is provided as a gas feed path in the
container 642. The heat exchanger pipe 645 is immersed in the
liquid nitrogen stored in the container 642, and one end thereof is
connected to a nitrogen gas supply source (not shown) via a mass
flow controller (MFC) 646 so that the nitrogen gas is supplied from
the nitrogen gas supply source. This causes the nitrogen gas to be
cooled to a temperature lower than a solidification point (freezing
point) of the DIW by the liquid nitrogen in the heat exchanger 641
and to be fed out as a cooling gas from the other end of the heat
exchanger pipe 645 to the cooling gas discharge nozzle 7 via an
on-off valve 647.
[0046] The cooling gas produced in this way is fed to the cooling
gas discharge nozzle 7. The cooling gas discharge nozzle 7 is, as
shown in FIG. 2, attached to a leading end part of a horizontally
extending first arm 71. A rear end part of this first arm 71 is
supported rotatably about a central axis of rotation J1 by a rotary
shaft 72 hanging down from a ceiling part of the processing chamber
1. A first arm elevating/rotating mechanism 73 is coupled to the
rotary shaft 72, and the rotary shaft 72 is driven and rotated
about the central axis of rotation J1 and driven and moved upward
and downward in response to an operation command from the control
unit 4. As a result, the cooling gas discharge nozzle 7 attached to
the leading end part of the first arm 71 moves above the substrate
surface Wf as shown in FIG. 4.
[0047] In this embodiment, a cold water discharge nozzle 8 is
constructed to be movable above the substrate surface Wf similar to
the cooling gas discharge nozzle 7. This cold water discharge
nozzle 8 supplies a liquid (corresponding to a "liquid to be
solidified" of the invention), which will form a liquid film and
has a temperature lower than normal temperature, e.g. DIW cooled
to, e.g. 0 to 2 degrees Celsius, preferably to about 0.5 degrees
Celsius, toward the surface Wf of the substrate W held by the spin
chuck 2. That is, the cold water discharge nozzle 8 is connected to
a cold water supply unit 65 which cools normal-temperature DIW
until about 0.5 degrees Celsius to product cold water and then
feeds the cold water to the cold water discharge nozzle 8. Note
that this cold water supply unit 65 includes a flow regulating
valve 651, a cooler 652 and an on-off valve 653 as shown in FIG. 3.
This flow regulating valve 651 feeds the normal-temperature DIW to
the cooler 652 while regulating the flow rate thereof with high
accuracy in response to a flow rate command from the control unit
4. Then, the cooler 652 cools the fed normal-temperature DIW to
about 0.5 degrees Celsius and the cold water (cooled DIW) is fed
out via the on-off valve 653.
[0048] To rotate the nozzle 8 receiving the supply of the cold
water about a central axis of rotation J2 and move it upward and
downward, a rear end part of a horizontally extending second arm 81
is supported rotatably about the central axis of rotation J2 by a
rotary shaft 82. On the other hand, the cold water discharge nozzle
8 is attached to a leading end part of the second arm 81 with a
discharge port (not shown) thereof faced downward. Further, a
second arm elevating/rotating mechanism 83 is coupled to the rotary
shaft 82, the rotary shaft 82 is driven and rotated about the
central axis of rotation J2 and driven and moved upward and
downward in response to an operation command from the control unit
4. As a result, the cold water discharge nozzle 8 attached to the
leading end part of the second arm 82 moves above the substrate
surface Wf as described below.
[0049] The cooling gas discharge nozzle 7 and the cold water
discharge nozzle 8 can respectively independently move relative to
the substrate W. That is, when the first arm elevating/rotating
mechanism 73 is driven and the first arm 71 is pivoted about the
central axis of rotation J1 as shown in FIG. 4 in response to an
operation command from the control unit 4, the cooling gas
discharge nozzle 7 attached to the first arm 71 horizontally moves
along a movement path T1 between a rotation center position Pc
corresponding to a position above the rotation center of the spin
base 23 and a standby position Ps1 laterally retracted from a
position facing the substrate W. That is, the first arm
elevating/rotating mechanism 73 moves the cooling gas discharge
nozzle 7 relative to the substrate W along the surface Wf of the
substrate W. However, in this embodiment, a movable range of the
cooling gas discharge nozzle 7 is narrowed as described later to
achieve the object of making the end-point temperature of the
frozen liquid film uniform and improve throughput.
[0050] Further, when the second arm elevating/rotating mechanism 83
is driven and the second arm 81 is pivoted about the central axis
of rotation J2 in response to an operation command from the control
unit 4, the cold water discharge nozzle 8 attached to the second
arm 81 horizontally moves along a movement path T2 between a
standby position Ps2 different from the standby position Ps1 of the
first arm 71 and the rotation center position Pc. That is, the
second arm elevating/rotating mechanism 83 moves the cold water
discharge nozzle 8 relative to the substrate W along the surface Wf
of the substrate W.
[0051] FIGS. 5A to 5C, 6A and 6B are views diagrammatically showing
operations of the substrate processing apparatus of FIG. 2. In this
apparatus, when an unprocessed substrate W is loaded into the
apparatus, the control unit 4 controls the respective parts of the
apparatus to perform a series of cleaning processes on the
substrate W. Here, the substrate W is loaded into the processing
chamber 1 with the surface Wf thereof faced upward beforehand and
held by the spin chuck 2, whereas the blocking member 9 is
retracted to an upper position where it does not interfere with the
arms 71, 81 while the back surface thereof is held facing the
substrate W as shown in FIG. 2.
[0052] After loading of the substrate W, the control unit 4 drives
the chuck rotating mechanism 22 to rotate the spin chuck 2 and
drives the second arm elevating/rotating mechanism 83 to move and
position the second arm 81 to the rotation center position Pc. In
this way, the cold water discharge nozzle 8 is positioned above the
rotation center of the substrate surface Wf, i.e. at the rotation
center position Pc as shown in FIG. 5A. Then, the control unit 4
opens the on-off valve 653 of the cooling gas supply unit 65 to
supply the low-temperature DIW to the substrate surface Wf from the
cold water discharge nozzle 8. A centrifugal force resulting from
the rotation of the substrate W acts on the DIW supplied to the
substrate surface Wf, the DIW is uniformly spread radially
outwardly of the substrate W, and a part thereof is spun off to the
outside of the substrate W. In this way, a liquid film (water film)
having a predetermined thickness is formed on the entire substrate
surface Wf by controlling the thickness of the liquid film to be
uniform over the entire substrate surface Wf. Note that, in forming
the liquid film, it is not an essential requirement to spin off a
part of the DIW supplied to the substrate surface Wf as described
above. For example, the liquid film may be formed on the substrate
surface Wf without spinning off the DIW from the substrate W in a
state where the rotation of the substrate W is stopped or the
substrate W is rotated at a relatively low speed.
[0053] In this state, a paddle-shaped liquid film LF having a
predetermined thickness is formed on the surface Wf of the
substrate W. When formation of the liquid film is finished, the
control unit 4 drives the second arm elevating/rotating mechanism
83 to move the second arm 81 to the standby position Psi and cause
it to wait. Further, after or simultaneously with the movement of
the second arm 81, the control unit 4 controls the cooling gas
supply unit 64 and the first arm elevating/rotating mechanism 73 to
supply the cooling gas to an initial position of the substrate
surface Wf (FIG. 5B). That is, the control unit 4 drives and
controls the first arm elevating/rotating mechanism 73 to move the
first arm 71 toward a position above a rotation center P(0) of the
substrate W, i.e. toward the rotation center position Pc at a
position sufficiently higher than the substrate W while controlling
the respective parts of the cooling gas supply unit 64 to supply
the cooling gas to the initial position of the substrate surface Wf
from the cooling gas discharge nozzle 7. Here, the "position
sufficiently higher than the substrate W" means such a height that
the cooling gas discharged from the nozzle 7 does not affect the
substrate W. When the cooling gas discharge nozzle 7 reaches a
position above a position P(Rin) short of the rotation center P(0)
of the substrate W, the control unit 4 drives and controls the
first arm elevating/rotating mechanism 73 to lower the cooling gas
discharge nozzle 7 to a position immediately above the position
P(Rin) short of the rotation center P(0) of the substrate W. In
this way, the cooling gas is supplied to the position P(Rin) of the
surface Wf of the rotating substrate W from a timing TM1 on. Note
that, in this specification, the rotation center of the substrate W
is denoted by "P(0)" and a position at a distance R from the
rotation center P(0) of the substrate surface Wf is denoted by
"P(R)" to specify the position of the cooling gas discharge nozzle
7. Particularly, the position of the substrate surface Wf
corresponding to the position right below the cooling gas discharge
nozzle 7 positioned at first as described above is referred to as
an "initial position P(Rin)". For example, in the apparatus for
processing the substrate W having a diameter of 300 mm, the value
of the distance R is between 0 mm and 150 mm. In this embodiment,
the distance Rin is set as follows.
W7/2<Rin<75 mm
where W7 denotes a diameter of a gas discharge port (not shown) of
the nozzle 7.
[0054] The cooling gas supplied to the initial position P(Rin) is
not only supplied to the initial position P(Rin), but also spreads
along the substrate surface Wf around the initial position P(Rin)
and a part thereof reaches as far as the rotation center P(0) of
the substrate W, with the result that the DIW adhering to an
initial region extending from the initial position P(Rin) to the
rotation center P(0) of the substrate W is solidified to form an
initial solidified region FR0 (initial solidifying step). Note that
it is difficult to immediately form the initial solidified region
FR0 even if the cooling gas is supplied to the substrate surface Wf
at the timing TM1 by arranging the nozzle 7 at the position right
above the initial position P(Rin). Thus, in this embodiment, the
nozzle 7 is stopped at the position right above the initial
position P(Rin) for a predetermined time .DELTA.T1 (=TM2-TM1). This
predetermined time .DELTA.T1 corresponds to a "first time" of the
present invention. Further, in freezing the liquid film LF, the
control unit 4 controls the mass flow controller 646 of the cooling
gas supply unit 64 to suppress the flow rate of the cooling gas
(i.e. cooling gas amount per unit time) to a value suitable for
freezing of the liquid film LF. Such suppression of the flow rate
of the cooling gas prevents the occurrence of a problem that the
substrate surface WF is partially dried and exposed and a problem
that a film thickness distribution is made nonuniform by wind
pressure and uniformity of the process cannot be ensured.
[0055] After the elapse of the predetermined time .DELTA.T1 from
the above timing TM1, the cooling gas discharge nozzle 7 is moved
in a direction D as shown in FIG. 6A, i.e. moved toward an outer
edge position of the substrate W while the supply of the cooling
gas is continued (nozzle moving step). This causes a solidified
region FR, which is solidified, to spread from the initial
solidified region FR0 toward the outer edge of the substrate W and
the entire liquid film on the substrate surface Wf to be frozen to
form the solidified film FF during the scan, for example, as shown
in FIG. 6B. The supply of the cooling gas may be stopped when the
cooling gas discharge nozzle 7 reaches a position above the outer
edge position of the substrate W, but the end-point temperature of
a solidified region FRe solidified near the outer edge of the
substrate W out of the solidified film FF may be possibly reduced
only to about 0 degrees Celsius since the amount of the cooling gas
supplied to the vicinity of the outer edge of the substrate W is
slightly less than that supplied to a region closer to the rotation
center. Accordingly, the supply of the cooling gas may be continued
while the cooling gas discharge nozzle 7 stays at the position
above the outer edge of the substrate W for a predetermined time
.DELTA.T2. Thus, the end-point temperature of the solidified film
FF on the entire substrate surface Wf can be made uniform by
sufficiently reducing the end-point temperature of the solidified
film FRe.
[0056] When the solidified film FF is formed by freezing the liquid
film LF in this way, the control unit 4 stops the discharge of the
cooling gas from the nozzle 7 and moves the first arm 71 to the
standby position Psi to retract the nozzle 7 from the substrate
surface Wf. Thereafter, the blocking member 9 is arranged proximate
to the substrate surface Wf and the high-temperature DIW heated to
about 80 degrees Celsius is supplied toward the frozen liquid film
on the substrate surface Wf from the nozzle 97 provided on the
blocking member 9 to thaw and remove the solidified film
(solidified body) FF (melting process). Subsequently, the
normal-temperature DIW as the rinsing liquid is supplied to the
substrate surface Wf to rinse the substrate W.
[0057] When the process thus far is performed, the DIW is supplied
to the surface of the substrate W in a state where the substrate W
is rotating while being sandwiched between the blocking member 9
and the spin base 23. Here, in parallel with the supply of the
high-temperature DIW and the normal-temperature DIW to the
substrate surface Wf, the high-temperature DIW and the
normal-temperature DIW may be supplied also from the nozzle 27.
Subsequently, the supply of the DIW to the substrate W is stopped
and a spin-drying process for drying the substrate W by high-speed
rotation is performed. That is, the substrate W is rotated at a
high speed while the nitrogen gas for drying supplied by the dry
gas supply unit 61 is discharged from the nozzle 97 provided on the
blocking member 9 and the nozzle 27 provided on the spin base 23,
whereby the DIW remaining on the substrate W is spun off to dry the
substrate W. When the drying process is finished, the already
processed substrate W is unloaded to complete the processes for one
substrate.
[0058] As described above, according to this embodiment, the DIW
adhering to the initial region including the initial position
P(Rin) and the rotation center P(0) can be solidified by arranging
the cooling gas discharge nozzle 7 above the initial position
P(Rin) distant from the rotation center P(0) of the substrate W
toward the outer edge of the substrate W and supplying the cooling
gas to the initial position P(Rin) of the rotating substrate W. For
example, after the cooling gas discharge nozzle 7 having an opening
of 31 [mm].times.46 [mm] as a gas discharge port is positioned
above the initial position P(65), i.e. above a position at a
distance of 65 [mm] from the rotation center P(0) of the substrate
W toward the outer edge, a nitrogen gas of -190 degrees Celsius is
supplied to the substrate surface Wf at a flow rate of 90 [L/min]
while the nozzle 7 is stayed there for a residence time of 3.4
[sec], whereby the initial solidified region FR0 is formed in a
central part of the liquid film LF (initial solidifying step). This
initial solidified region FR0 is a region solidified by the cooling
gas spreading around the initial position P(65) along the substrate
surface Wf and so formed on the substrate surface Wf as to
continuously extend from the initial position P(65) to the rotation
center P(0). The initial solidified region FR0 has a substantially
circular shape centered on the central axis of rotation (vertical
axis) AO in a plan view from above. This point is also confirmed in
an example to be described later.
[0059] Following formation of the initial solidified region FR0 by
the supply of the cooling gas, the nozzle 7 is moved from the
position above the initial position P(65) to a position above the
outer edge part of the substrate W for about 9.4 seconds (nozzle
moving step) while supplying the cooling gas from the nozzle 7.
This makes a range to be solidified spread from the initial region
toward the outer edge of the substrate W, so as that all the DIW
(liquid to be solidified) adhering to the substrate surface Wf is
solidified to freeze the entire liquid film LF. By setting the
position where the cooling gas is first supplied from the nozzle 7
at the side closer to the outer edge than the rotation center P(0)
of the substrate W, the end-point temperature of the solidified
film (solidified body) FF could be made uniform over the entire
surface of the substrate W and in-plane uniformity of the removal
rate could be improved. Further, the movable range of the nozzle 7
is narrowed and, as compared with the conventional technique in
which the position where the cooling gas is first supplied is set
above the rotation center P(0), a time required for the nozzle
movement can be shortened and throughput can be increased.
Furthermore, by reducing the moving speed of the nozzle 7 by as
much as the movable range of the nozzle 7 is narrowed, the cooling
gas is supplied to the respective parts of the substrate surface Wf
for a longer time and the end-point temperature can be further
reduced. In this case, the particle removal rate can be further
improved. This point is also confirmed in the example to be
described later.
[0060] After being moved to a position P(150) near the outer edge
of the substrate W, the cooling gas discharge nozzle 7 is caused to
stay at this position for the predetermined time .DELTA.T2, e.g.
5.7 [sec] and continues to supply the cooling gas. Thus, the
end-point temperature of the solidified region FRe can be
sufficiently reduced and the end-point temperature of the
solidified film FF on the entire substrate surface Wf becomes
uniform to improve the in-plane uniformity of the removal rate.
[0061] As described above, in this embodiment, the spin chuck 2
corresponds to a "substrate holder" of the invention, and the chuck
rotating mechanism 22 corresponds to a "rotator" of the invention.
Further, the cooling gas discharge nozzle 7 and the cooling gas
supply unit 64 function as a "cooling gas supplier" of the
invention and the first am 71 and the first arm elevating/rotating
mechanism 73 function as a "mover" of the invention.
[0062] Note that the invention is not limited to the above
embodiment and various changes other than the aforementioned ones
can be made without departing from the gist of the invention. For
example, in the above embodiment, the position P(65) at a distance
of 65 [mm] from the rotation center P(0) of the substrate W toward
the outer edge is set as the initial position, and the cooling gas
discharge nozzle 7 is arranged above this position to form the
initial solidified region FR0 (initial solidifying step). However,
the initial position P(Rin) is not limited to this and only has to
be closer to the outer edge than the rotation center P(0) of the
substrate W and closer to the rotation center of the substrate W
than a middle position between the rotation center P(0) of the
substrate W and the outer edge P(150) of the substrate W. More
preferably, the initial position P(Rin) is closer to the outer edge
than a position P(W7/2).
[0063] Although the cooling gas discharge nozzle 7 is arranged
above the initial position by being moved and relatively moved
toward the outer edge of the substrate from the position above the
initial position, the substrate W may be moved instead of or
together with the cooling gas discharge nozzle 7.
[0064] Further, although the liquid film is formed by the DIW in
the above embodiment, the liquid for forming the liquid film, i.e.
the liquid to be solidified is not limited to this. For example,
carbonated water, hydrogenated water, low-concentration (e.g. about
1 ppm) ammonia water, low-concentration hydrochloric acid or the
like may be used or a small amount of surfactant may be added to
the DIW.
[0065] Although the dry gas (nitrogen gas) is supplied to the dry
gas supply unit 61 and the cooling gas supply unit 64 from the same
nitrogen gas supply source in the above embodiment, it is not
limited to the nitrogen gas. For example, the dry gas and the
cooling gas may be different types of gases each other.
[0066] Further, although the nitrogen gas supply source, the DIW
supply source and the liquid nitrogen supply source are all built
in the substrate processing apparatus of the above embodiment,
these supply sources may be provided outside the apparatus. For
example, existing supply sources in a factory may be utilized.
Further, if there is an existing facility for cooling these,
liquids and gases cooled by this facility may be utilized.
[0067] Furthermore, although the substrate processing apparatus of
the above embodiment includes the blocking member 9 arranged above
and proximate to the substrate W, the invention is also applicable
to an apparatus including no blocking member. Further, although the
substrate W is held by the chuck pins 24 held in contact with the
peripheral edge part of the substrate W in the apparatus of this
embodiment, a substrate holding method is not limited to this and
the invention can be also applied to an apparatus in which a
substrate is held by another method.
[0068] In the invention (substrate processing method and substrate
processing apparatus) according to the above embodiment, the
cooling gas is supplied to the initial position from the nozzle
arranged above the initial position distant from the rotation
center of the substrate toward the outer edge of the substrate. If
the cooling gas is supplied to the initial position of the
substrate in this way, it spreads around the initial position along
the substrate surface and a part thereof reaches even the rotation
center of the substrate. As a result, the liquid to be solidified
adhering to the initial region extending from the initial position
to the rotation center of the substrate is solidified. When the
nozzle is relatively moved toward the outer edge of the substrate
thereafter while supplying the cooling gas, the range to be
solidified spreads from the initial region toward the outer edge of
the substrate and all the liquid to be solidified adhering to the
substrate surface is solidified. By setting the position, where the
cooling gas is first supplied from the nozzle, at the side closer
to the outer edge than the rotation center of the substrate in this
way, the temperature of the solidified liquid can be made uniform
over the entire surface of the substrate and the in-plane
uniformity of the removal rate can be improved. Further, since the
movable range of the nozzle is narrower than in the conventional
technique, the time required for the nozzle movement is shortened
to improve throughput.
[0069] Here, merely in terms of narrowing the movable range of the
nozzle, it is preferable to set the initial position closer to the
outer edge of the substrate. However, if the initial position is
too close to the outer edge of the substrate, it is difficult to
solidify the liquid to be solidified on the rotation center of the
substrate by the first supply of the cooling gas. Thus, as shown in
an experimental result to be described later, solidification
progresses from the outer edge side toward the rotation center side
near the rotation center of the substrate and the temperature of
the liquid to be solidified is not made uniform over the entire
substrate surface to impair the in-plane uniformity of the removal
rate. Therefore, it is preferable to set the initial position in a
range where the liquid to be solidified adhering to the initial
region can be solidified by the cooling gas supplied from the
nozzle arranged above the initial position, e.g. closer to the
rotation center of the substrate than the middle position between
the rotation center of the substrate and the outer edge of the
substrate.
[0070] Conversely, if the initial position is too close to the
rotation center of the substrate, the temperature at the rotation
center is excessively reduced to make the end-point temperature in
the substrate surface nonuniform, the nozzle movable range is
widened and it becomes difficult to improve throughput similar to
the conventional technique. Therefore, a distance from the rotation
center of the substrate to the initial position is preferably equal
to or larger than half the diameter of the gas discharge port for
discharging the cooling gas from the leading end part of the
nozzle.
[0071] Since it is difficult to solidify the liquid to be
solidified in the initial region immediately after the cooling gas
is supplied to the initial position from the nozzle arranged above
the initial position, a relative movement of the nozzle is
preferably started after the elapse of the first time from the
supply of the cooling gas to the initial position. Further, by
stopping the supply of the cooling gas after the elapse of the
second time after the movement of the nozzle to the position above
the vicinity of the outer edge of the substrate is completed, the
end-point temperature of the liquid solidified near the outer edge
of the substrate can be sufficiently reduced. This can further
improve temperature uniformity of the liquid to be solidified over
the entire substrate surface and the in-plane uniformity of the
removal rate.
[0072] Next, an example of the invention and comparative examples
will be shown. The invention is not limited by the following
example and comparative examples and can be, of course, carried out
by appropriately making changes within the scope conformable to the
gist described above and below and all of such changes are included
in the technical scope of the invention.
[0073] Here, the shape and size of the initial solidified region
FR0 were verified while the first position of the cooling gas
discharge nozzle 7 was changed as shown in FIGS. 7A to 7C, 8A to
8C. That is, the initial solidified regions FR0 were respectively
observed when the cooling gas discharge nozzle 7 was arranged:
[0074] above the rotation center P(0) of the substrate W;
[0075] above the position P(20) of the substrate W;
[0076] above the position P(40) of the substrate W;
[0077] above the position P(65) of the substrate W;
[0078] above the position P(80) of the substrate W; and
[0079] above the position P(100) of the substrate W,
and a nitrogen gas of -190 degrees Celsius was supplied as the
cooling gas to the substrate surface Wf at a flow rate of 90
[L/min] while the cooling gas discharge nozzle 7 was caused to stay
for 2 seconds. As a result, when the cooling gas discharge nozzle 7
was positioned above the rotation center P(0), the position P(20),
the position P(40) and the position (65) of the substrate W,
substantially circular initial solidified regions FR0 including the
initial position and having a radius of 40 [mm], 70 [mm], 80 [mm]
and 105 [mm] centered on the central axis of rotation (vertical
axis) OA of the substrate W in plan views were obtained (FIGS. 7A
to 7C, FIG. 8A). When the cooling gas discharge nozzle 7 was moved
toward the outer edge of the substrate W while continuing to supply
the cooling gas after formation of the initial solidified region
FR0, the initial solidified region FR0 spreads from the rotation
center side toward the outer edge side and the solidified film FF
was formed on the entire substrate surface Wf. On the contrary,
when the cooling gas discharge nozzle 7 was positioned above the
position P(80) and the position P(100) distant from the above
positions toward the outer edge, the liquid film could not be
solidified near the rotation center and doughnut-shaped initial
solidified regions FR0 in plan views were obtained (FIGS. 8B and
8C). When the cooling gas discharge nozzle 7 was moved toward the
outer edge of the substrate W while continuing to supply the
cooling gas after formation of the initial solidified region FR0,
an outer peripheral side of the initial solidified region FR0
spreads toward the outer edge side and, on the other hand, an inner
peripheral side thereof spreads toward the rotation center with a
slight delay, whereby the solidified film FF was formed on the
entire substrate surface Wf.
[0080] When end-point temperature distributions of the solidified
films FF formed on the substrate surfaces Wf were measured for the
substrates W on which the initial position P(Rin) was set at the
rotation center P(0), the position P(65) and the position (100) out
of the substrates W on which the solidified films FF were obtained
in this way, a result shown in FIGS. 9A to 9C was obtained. Marks
in FIG. 9A, i.e. R0 (X A), R30 (X B), R60 (X C), R90 (X D), R120 (X
E) and R140 (X F) respectively indicate surface temperatures at
positions at distances of 0 [mm], 30 [mm], 60 [mm], 90 [mm], 120
[mm] and 140 [mm] in a radial direction. As is clear from FIG. 9A,
when the initial position P(Rin) was set at the rotation center
P(0) of the substrate W, i.e. in the conventional technique, the
end-point temperature at the rotation center is drastically lower
than those at the other positions, the end-point temperature
increases with distance toward the outer edge and the temperature
near the outer edge is drastically higher than near the rotation
center. Further, when the initial position P(Rin) was set at the
position P(100), the end-point temperature is relatively low near
the outer edge and drastically higher near the rotation center than
near the outer edge. On the contrary, when the initial position
P(Rin) was set at the position P(65), the end-point temperature is
slightly higher near the outer edge, but relatively equally low in
the plane of the substrate surface Wf.
[0081] After the same melting process, rinsing process and drying
process as in the above embodiment were performed for the
substrates W having end-point temperature distributions shown in
FIGS. 9A to 9C, particle removal rates at respective parts of the
respective substrates W were measured to obtain a result shown in
FIG. 10. As shown in FIG. 10, when the initial position P(Rin) was
set at the rotation center P(0) and the position P(100), the
particle removal rate is low near the respective parts where the
temperature of the solidified region FF was high and no sufficient
in-plane uniformity was obtained. On the contrary, when the initial
position P(Rin) was set at the position P(65), a uniform and high
particle removal rate was obtained over the entire substrate
surface Wf. This coincides with the result of the end-point
temperature distribution shown in FIG. 9B.
[0082] As described above, particles and the like can be removed
with excellent in-plane uniformity by moving the nozzle 7 toward
the outer edge while supplying the cooling gas from the nozzle 7
after the initial solidifying step is performed with the nozzle 7
arranged above the initial position distant from the rotation
center P(0) of the substrate W toward the outer edge of the
substrate W so that the DIW (liquid to be solidified) adhering to
the initial region extending from the initial position to the
rotation center P(0) of the substrate can be solidified.
[0083] Although the invention has been described with reference to
specific embodiments, this description is not meant to be construed
in a limiting sense. Various modifications of the disclosed
embodiment, as well as other embodiments of the present invention,
will become apparent to persons skilled in the art upon reference
to the description of the invention. It is therefore contemplated
that the appended claims will cover any such modifications or
embodiments as fall within the true scope of the invention.
* * * * *